Hemiplegia contributes significantly to the physical disability and impaired quality of life of stroke survivors. However, there are no rehabilitation techniques that have been shown to influence the motor neuroplasticity of a healing brain after stroke. Present rehabilitation strategies emphasize compensatory training of the unimpaired extremities to maximize function, and prevention of complications of immobility. The broad goal of this project is to develop strategies to facilitate the motor recovery of stroke survivors, and thereby maximize their function and quality of life Previous studies have suggested that repetitive exercises facilitated by electromyograph (EMG)-controlled neuromuscular stimulation enhance the motor recovery of stroke survivors. However, those studies were poorly controlled, and mechanisms of action were not addressed. The aims of this project are to 1) assess the efficacy of EMG-controlled, neuromuscular stimulation in enhancing the upper-extremity motor recovery of chronic stroke survivors, and 2) determine whether EMG-controlled neuromuscular stimulation mediates its effect on motor recovery via central mechanisms. Phase I of the study will identify neurophysiologic measures of brain function that correlate with objective measures of motor impairment. Phase II will consist of a single-blinded, randomized clinical trial to assess the effects of EMG-controlled neuromuscular stimulation on objective measures of motor impairment and measures of central motor function identified in phase I. This study will demonstrate that EMG-controlled neuromuscular stimulation enhances the motor recovery of chronic stroke survivors, and that the motor recovery is mediated by central mechanisms. The proposed intervention may be effective for acute stroke survivors and persons with other forms of cerebral motor dysfunction such as traumatic brain injury, cerebral palsy and multiple sclerosis. EMG-controlled neuromuscular stimulation may also be effective for lower extremity motor recovery. Finally, techniques developed for assessing central motor function may be useful for evaluating other interventions directed at stroke rehabilitation.